Hmmmm, I can understand that you don't want to play with the original music (those AGI-sounds always give me headaches too if I don't use that SB-patch)
To be able to solve this, we first need to know which KQ4 you have, the AGI-version or the SCI-version (AGI-version has typing while walking, SCI-version has a bar that pops up when you start talking)
Along with that, is that midi driver you got a windows-driver or something specially for those games?
-Kon-Tiki-